docs: def eval_hessian(self, ordered_parameters=[], **parameters):
          """
          :return: Zeros with the shape of the Hessian of the model.
          """
          result = super(HessianObjectiveJacApprox, self).__call__(
              ordered_parameters, **parameters
          )
          num_params = len(self.model.params)
          return [np.broadcast_to(
                      np.zeros_like(comp),
                      (num_params, num_params) + comp.shape
                  ) for comp in result]